Modular anchor bone fusion cage

ABSTRACT

A modular anchor bone fusion cage is provided. The cage includes a spacer configured to fit into a space between the faces of two bones that are to be fused together. A fusion plate having at least a main body portion is coupled to the spacer by a connector. Fasteners extend through the fusion plate to engage the bone. At least some of the fasteners also extend through the spacer to engage the opposed faces of the bone. A cover plate is coupled to the fusion plate to inhibit the fasteners from backing out prior to fusion of the bones.

BACKGROUND

The human spine contains a series of bony segments separated by discsand coupled together with muscle, ligaments, and other connectivetissues. A large number of ailments may afflict one or more of thesecomponents. One exemplary ailment generally occurs with age as thespinal discs begin to break down, or degenerate resulting in the loss offluid in the discs, and consequently, the discs become less flexible.Likewise, the discs become thinner allowing the vertebrae to move closertogether. Degeneration also may result in tears or cracks in the outerlayer, or annulus, of the disc. Degeneration of the annulus may allowthe disc to begin to bulge outwardly. In more severe cases, the innermaterial of the disc, or nucleus, may extrude out of the disc. Inaddition to degenerative changes in the disc, the spine may undergochanges due to trauma from automobile accidents, falls, lifting, andother activities. Furthermore, in a process known as spinal stenosis,the spinal canal narrows due to excessive bone growth, thickening oftissue in the canal (such as ligament), or both. In all of theseconditions, the spaces through which the spinal cord and the spinalnerve roots pass may become narrowed leading to pressure on the nervetissue which can cause pain, numbness, weakness, or even paralysis invarious parts of the body. Finally, the facet joints between adjacentvertebrae may degenerate and cause localized and/or radiating pain. Allof the above conditions, as well as others not specifically mentioned,are collectively referred to herein as spine disease.

Conventionally, surgeons treat spine disease by attempting to restorethe normal spacing between adjacent vertebrae. This may be sufficient torelieve pressure from affected nerve tissue. However, it is oftennecessary to surgically remove disc material, bone, or other tissuesthat impinge on the nerve tissue and/or to debride the facet joints.Most often, the restoration of vertebral spacing is accomplished byinserting a rigid spacer made of bone, metal, or plastic into the discspace between the adjacent vertebrae and allowing the vertebrae to growtogether, or fuse, into a single piece of bone. The vertebrae aretypically stabilized during this fusion process with the use of boneplates and/or pedicle screws fastened to the adjacent vertebrae.

Although techniques for placing intervertebral spacers, plates, andpedicle screw fixation systems have become less invasive in recentyears, they still require the placement of hardware deep within thesurgical site adjacent to the spine. The hardware is frequently relatedto the intervertebral spacer, itself, along with additional hardware toimmobilize the vertebral segment associated with the fusion. Theadditional hardware also inhibits the spacer from exiting the space.Recovery from such surgery can require several days of hospitalizationand long, slow rehabilitation to normal activity levels.

Thus, it would be desirable to provide an implantable intervertebralspacer that presented as low a profile as possible while still providingsufficient hardware to facilitate immobilizing the vertebral segmentbeing fused.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified and incomplete manner highlighting some of the aspectsfurther described in the Detailed Description. This Summary, and theforegoing Background, is not intended to identify key aspects ofessential aspects of the claimed subject matter. Moreover, this Summaryis not intended for use as an aid in determining the scope of theclaimed subject matter.

In some aspects of the technology disclosed by the present application,an implant is provided. The implant generally relates to fusing twoboney segments together using as low a profile as possible. In oneaspect of the technology, the implant has a spacer and a fusion platethat may be coupled to the spacer. The spacer is configured to fitbetween the two boney segments and promote fusion therebetween. Thefusion plate couples to a rear (sometimes an anterior) portion of thespacer. The fusion plate includes a main body portion generallyconforming in size and shape to the rear portion of the spacer and afirst extension side extending from the main body portion of the fusionplate to overlie a portion of the bones to be fused together. Theimplant is coupled by fasteners extending through the fusion plate. Someof the fasteners may intersect with the rear portion of the spacer andextent through the top or bottom portion of the spacer. Some of thefasteners may extend through the fusion plate directly into the bone,although a portion of the fastener may interest with the rear portion ofthe spacer.

In still other aspects of the technology provided by the presentapplication a cover plate may further be provided. The cover plate maybe coupled to the fusion plate to inhibit the fasteners from reversethreading to promote the immobilization of the boney segment.

In certain embodiments, the spacer will be provided with a cavity wherethe main body portion of the fusion plate fits within the cavity toallow a portion of the fusion plate to reside in the space between theboney segments. In these embodiments, the first extension side willangle or flare from the main body portion of the fusion plate to allowthe first extension side to reside along one of the adjacent bones. Thefirst extension side may be straight, curved, sinusoidal, or acombination thereof.

In certain embodiments provided by the technology of the presentapplication the spacer will have a spacer bore that is coupled to afirst end of a connector. In certain aspects, the spacer bore will havea thread that cooperatively engages an external thread of the connector,such as, for example, a set screw. The fusion plate will correspondinglyhave an aligned plate bore that is coupled to a second end of theconnector. In certain aspects, the plate bore will have a shoulder andthe second end of the connector will have a plurality of protrusionswith outturned lips. The second end will be elastically deformable toform a snap fit between the outturned lips of the second end of theconnector and the shoulder of the plate bore. In certain aspects a coverplate will further have a cover plate bore with a thread. The coverplate bore aligns with the plate bore. A connecting pin couples thecover plate to the fusion plate. In certain aspects of the technology,the connecting pin has a head and a shaft. The shaft has a first threadproximate to the head and a second thread distal to the head. Anintermediate portion of the shaft may be non-threaded to separate thefirst thread from the second thread. The second thread may cooperativelyengage an internal thread of the connector and the first thread maycooperatively engage the thread of the cover plate bore to couple thecover plate to the fusion plate.

This summary provides only a general outline of some aspects of thetechnology disclosed herein. The above and other aspects of thetechnology of the present application will be apparent afterconsideration of the Detailed Description and Figures herein. It is tobe understood, however, that the scope of the application shall bedetermined by the claims as issued and not by whether given subjectmatter addresses any or all issues noted in the Background or includesany features or aspects highlighted in the Summary.

BRIEF DESCRIPTION OF THE DRAWINGS

Various examples of the present invention will be discussed withreference to the appended drawings. These drawings depict onlyillustrative examples of the invention and are not to be consideredlimiting of its scope.

FIG. 1 is a side view of three adjacent vertebra having an implantconsistent with the technology of the present application;

FIG. 2 is perspective view of a spacer consistent with the technology ofthe present application;

FIG. 3 is a top plan view of the spacer of FIG. 2;

FIG. 4 is a cross-sectional view along line A-A of FIG. 3;

FIG. 5 is rearward portion elevation view of the spacer of FIG. 2;

FIG. 6 is a perspective view of a fusion plate consistent with thetechnology of the present application;

FIG. 7 is another perspective view of the fusion plate of FIG. 6;

FIG. 8 is perspective view of a threaded connector shown in FIG. 7consistent with the technology of the present application;

FIG. 9 is perspective view of a fastener consistent with the technologyof the present application;

FIG. 10 is a perspective view of a lock usable with the technology ofthe present application;

FIG. 11 is a perspective view of a cover plate consistent with thetechnology of the present application;

FIG. 12 is perspective view of a connector pin consistent with thetechnology of the present application;

FIG. 13 is a perspective view of an implant consistent with thetechnology of the present application;

FIG. 14 is a perspective view of a fusion plate consistent with thetechnology of the present application;

FIG. 15 is a side elevation view of the fusion plate of FIG. 14;

FIG. 16 is a perspective view of a cover plate consistent with thetechnology of the present application;

FIG. 17 is a side elevation view of the cover plate of FIG. 16;

FIG. 18 is a perspective view of an implant consistent with thetechnology of the present application;

FIG. 19 is a perspective view of a fusion plate consistent with thetechnology of the present application;

FIG. 20 is a side elevation view of the fusion plate of FIG. 19;

FIG. 21 is a perspective view of a cover plate consistent with thetechnology of the present application;

FIG. 22 is a side elevation view of the cover plate of FIG. 21; and

FIG. 23 is a perspective view of an implant consistent with thetechnology of the present application.

DETAILED DESCRIPTION

The technology of the present patent application will now be explainedwith reference to various figures and the like. While the technology ofthe present application is described with respect to implants thatfacilitate spinal fusion, such as, for example, anterior lumbarinterbody fusion (ALIF) implants, one of ordinary skill in the art wouldrecognize on reading the disclosure that the technology is applicable toother implants. For example, the technology as described herein may beused for implants to facilitate fusion of other spinal fusions, such asa transforaminal lumbar interbody fusion (TLIF), anterior cervicaldiscectomy (ACD), posterior lumbar interbody fusion (PLIF), lateralthoracolumbar fusions, and other skeletal fusions, such as long bones orthe like. Moreover, the technology of the present patent applicationwill be described with reference to certain exemplary embodimentsherein. The word “exemplary” is used herein to mean “serving as anexample, instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or examples absent a specificindication that such an embodiment or example is preferred oradvantageous over other embodiments. Moreover, in certain instances,only a single “exemplary” embodiment is provided. A single example isnot necessarily to be construed as the only embodiment. The detaileddescription includes specific details for the purpose of providing athorough understanding of the technology of the present patentapplication. However, on reading the disclosure, it will be apparent tothose skilled in the art that the technology of the present patentapplication may be practiced with or without these specific details. Insome descriptions herein, generally understood structures and devicesmay be shown in diagrams to aid in understanding the technology of thepresent patent application without obscuring the technology herein.

Referring first to FIG. 1, three vertebrae 40, 42, and 44 are provided.Each of the vertebrae 40, 42, and 44 have an anterior side 46, aposterior side 48 and lateral sides 50 (only one shown). The threevertebrae 40, 42, and 44 each have a spinous process 60.

In a normal spine, discs would reside between each of the endplates 55of vertebrae 40 and 42, and vertebrae 42 and 44. The endplates 55 formopposed bony surfaces for spinal application, but use of the technologyto be described herein is applicable to any bony segments to be fusedacross opposed facing bony surfaces. For convenience of illustration,the discs are not included in the figures. However, injury, age,disease, or other trauma may cause the discs to degenerate for onereason or another. To restore proper height to a disc, for example, asurgeon would remove all or a portion of the disc and replace it with aspacer. For example, as shown in FIG. 1, a spacer 52 may be surgicallyimplanted in the space between vertebrae 40 and 42. As shown, spacer 52is implanted from the anterior side of the patient. A fusion plate 54,as will be explained further below, is coupled to the spacer 52 andextends over only one of the vertebrae 40 and 42 in the exemplaryembodiment of the technology shown in FIG. 1. While shown in a spinalapplication, the technology of the present application is usable tofacilitate the fusion of other bones.

Referring now to FIGS. 2 and 3, an exemplary spacer 52 is shown. Thespacer 52 is generally shaped to fit within the intervertebral space andhas a forward portion 102, which may be referred to as a posteriorportion 102, a rearward portion 104, which may be referred to as ananterior portion 104, a top portion 106, which may be referred to as asuperior portion 106, a bottom portion 108, which may be referred to asan inferior portion 108, and side portions 110. The spacer 52 may haveapertures 112 to receive radio opaque plugs 114, which are useful fortracking when using computer assisted surgery, and as marking forfluoroscopy or other imaging techniques in which the bulk of spacer 52may be difficult to visualize. The orientation of the front (posterior),rear (anterior), left, right, top (superior), and bottom (inferior), orthe like are provided for reference and should not be construed to limitthe technology of the present application. The spacer 52 is provided tofit entirely in the intervertebral space; although in certainembodiments, the rearward portion 104 may extend beyond the anteriorends of the vertebrae.

As shown in FIG. 3, the forward portion 102 is shaped to have a concave,convex, and concave portion forming a recess 118. The recess 118 isconfigured to avoid the dura in spinal applications, but would not benecessary for other applications of the technology. The rearward portion104 is generally shaped to have a concave shape consistent with theanterior aspect of the vertebrae 40, 42 between which it is implanted.The rearward portion 104 comprises a cavity 120 having a depth D₁ toreceive a fusion plate as will be explained further below. The sideportions 110 provide a concave portion transitioning between the forwardportion 102 and the rearward portion 104. The spacer 52, as shown, has afirst and a second void 122, 124 separated by a central strut 126providing the spacer 52 with a vaguely “B” shape. Other shapes and typesof spacers 52 are possible, such as, for example, other fusion cages,dowels, and the like. The first void 122 and second void 124 may bepacked with material to facilitate bone growth and fusion of thevertebrae 40, 42. The first and second voids 122, 124 are both generallygreater than 20% of the surface area of the spacer 52. Alternatively tothe large first and second voids 122, 124, a large number of smallerbone growth channels are possible.

A number of protrusions 116 may be provided on the top portion 106, thebottom portion 108, or a combination thereof. As best seen in FIG. 4,which is a cross-sectional view across line A-A in FIG. 3, theprotrusions 116 form a generally shark-tooth shape that angles from theforward portion 102 towards the rearward portion 104. The protrusions116 generally resist movement of the spacer 52 out of the intervertebralspace between vertebrae 40, 42. As shown in the cross-section, the topportion 106 and bottom portion 108 may be convex shapes providing thespacer 52 with a bi-convex shape from the forward portion 102 to therearward portion 104 forming a dome shape close to a lordotic curvatureor positioning of the vertebrae. The forward portion 102 (or posteriorportion 102) has a taper 128 to facilitate insertion of the spacer 52.The forward portion 102 expands symmetrically on both sides to a thickersection. The spacer 52, in this exemplary embodiment, is generallythickest in the rearward portion 104, but generally forward of cavity120. Instead of a bi-convex, domed shape, the spacer 52 may form a moreconventional wedge shape or have a planar top portion 106, a planarbottom portion 108, or a combination thereof.

Still with reference to FIG. 4, the protrusion 116 are formed by a firstsurface 130 forming an obtuse angle with a surface of the spacer 52. Thefirst surface 130 extends to an engaging surface 132 of the protrusion116. The engaging surface 132 is adapted to engage the endplates of thevertebrae 40, 42. The engaging surface 132 may be formed to a linecontact, a point contact, or to a flat or convex surface formedgenerally parallel to the body surface. In particular, the engagingsurface 132 may be formed and shaped to conform to the anatomical shapeof the associated endplates. A surface formed by connecting the engagingsurface 132 on the top and bottom portion 106, 108, may be shaped toconform to the anatomical shape of the associated endplates as well. Asecond surface 134 extends from the engaging surface 132 back to thesurface of the spacer 52. The second surface 134 also forms an obtuseangle, but may form a right angle or be slightly undercut. Theprotrusions 116 are generally of a unified construction with the body.The protrusions 116 are separated by a flat or scooped gap 136 betweeneach protrusion and generally extend over the entire superior andinferior surface of the implant. However, the forward portion 102 has aportion without protrusions, generally associated with the taper 128. Ina particular embodiment, protrusions 116 have a shape as generallydisclosed in U.S. Pat. No. 7,041,137 or 7,427,294, both of which areassigned to the assignee of the present application and the completedisclosures of which are incorporated herein by reference for allpurposes.

Referring now to FIG. 5, an elevation view of the rearward portion 104of spacer 52 is provided. Cavity 120 has a length L₁ and a height H₁,and is sized to cooperatively engage a fusion plate, which will beexplained further below. A threaded spacer bore 138 is in the cavity120. The threaded spacer bore 138 is used, as will be explained furtherbelow, to couple the spacer 52 and the fusion plate. The threaded spacerbore 138 may have an undercut. The threaded spacer bore 138 extends intothe central strut 126. The threaded spacer bore 138 has a first threadT₁. The cavity 120 has an upper edge 140 at a transition to the topportion 106 and a lower edge 142 at a transition to the bottom portion108. A spacer channel 144 is accessible from cavity 120 and exists ineach of the upper edge 140 and the lower edge 142. As shown, there aretwo spacer channels 144 proximate the upper edge 140 and two spacerchannels 144 proximate the lower edge 142. The spacer channels 144 areshown as having generally half-cylindrical shapes, such as a half pipe,U shapes, or V shapes that provides a guide for a fastener, which willbe explained further below. The spacer channels 144 may be bores aswell. The spacer channels 144 are shown on both the upper and lower edge140, 142 of the spacer 52. In certain aspects of the technology, thespacer channels 144 may only be oriented on the upper edge 140 or thelower edge 142.

As can be appreciated on reading the above, the spacer 52 is providedwith a length L₂ and a height H₁ to provide an implant having areasonably low profile to fit within the intervertebral space with thespacing desired by the surgeon. To anchor the spacer 52 to the superiorand inferior vertebrae, a fusion plate 54 (FIG. 1) is provided incertain aspects of the technology of the present application. In manyembodiments, the plate provided has as low a profile as possible.

Referring now to FIGS. 6 and 7, a low profile fusion plate 200consistent with the technology of the present application is provided.The low profile fusion plate 200 has a forward face 202 and a rearwardface 204 opposite the forward face 202. A sidewall 206 extends betweenthe forward face 202 and the rearward face 204. The edges of sidewall206 may be beveled or chamfered to reduce trauma. The low profile fusionplate 200 has a length L₃, a height H₂, and a depth D₂ to allow lowprofile fusion plate 200 to cooperatively engage cavity 120. The lowprofile fusion plate 200 has a plurality of fastener bores 208 thatgenerally correspond to the spacer channels 144 associated with thespacer 52. The fastener bores 208 have an internal sidewall 210 forminga concave surface for cooperative engagement with a fastener as will bedescribed below. In some embodiments, the concave surface formed byinternal sidewall 210 generally is a spherical shape or curvature. Theforward face 202 may have a plurality of protrusions 212 extendingtherefrom to cooperatively engage the spacer channels 144. As shown, theprotrusions 212 are generally shaped as partial cylindrical surfaces.

The low profile fusion plate 200 further comprises a plate bore 214. Theplate bore 214 is adapted to be aligned with threaded spacer bore 138.The plate bore 214 has an inner wall 216 and an outer wall 218 (shown inFIG. 7) extending from forward face 202 into threaded spacer bore 138.The plate bore 214 at a distal end thereof may have an outwardly turnedlip 220. The plate bore 214 may be fitted to the spacer 52 by causingoutwardly turned lip 220 to engage an undercut in the threaded spacerbore 138. Moreover, the inner wall 216 may be provided with a shoulder222, which may be a ledge extending into the bore or a groove extendinginto the wall.

In one aspect of the technology, the low profile fusion plate 200 iscoupled to the spacer 52 using a threaded connector 224 as shown inFIGS. 7 and 8. The threaded connector 224 has a slotted head end 226.The slots form a number of compressible protrusions 228 with outwardlyturned lips 230. The threaded connector 224 also has a threaded shaft232. The threaded shaft 232 has an outer thread T₂ adapted tocooperatively engage the threads T₁ of threaded spacer bore 138. Thethreaded connector 224 also comprises an inner threaded bore 234 havinginner threads T₃ as will be explained further below.

The threaded connector 224 is coupled to the low profile fusion plate200 by inserting the slotted head end 226 of the threaded connector 224into the plate bore 214. The head end compresses until the outwardlyturned lips 230 extend past the shoulder 222, at which point the slottedhead expands to form a snap lock between the threaded connector 224 andthe low profile fusion plate 200. In alternative embodiments, thethreaded connector 224 is coupled to the fusion plate 200 with a C-ring,a split ring, or the like. The threaded connector 224 is next threadedinto the threaded spacer bore 138 to couple the low profile plate to thespacer 52.

The spacer 52 and the low profile fusion plate 200 are coupled to thesuperior and inferior vertebrae in this exemplary aspect by a pluralityof fasteners 236. The fasteners 236 may be any conventional fasteners,such as, for example, a bone screw 236 as shown in FIG. 9. The bonescrew 236 may comprise a head 238 and a shaft 240 having threads T. Thehead 238 may be provided with a convex lower surface 242 tocooperatively engage the internal sidewall 210 of the fastener bores 208in the low profile fusion plate 200. The fasteners 236 are adapted to bethreaded into the endplates of the vertebrae 40, 42 by extending fromthe fastener bores into the rearward portion 104 of the spacer 52 andout of at least one of the top portion 106 or bottom portion 108.

The fasteners 236, as is conventionally known, may have a tendency toreverse thread or back-out of the vertebrae 40, 42, the spacer 52, andthe fusion plate 54. A lock may be provided to inhibit the fasteners 236from reverse threading. In certain aspects of the technology, the lockis similar to bushing 244 as shown in FIG. 10. The bushing 244 comprisesa top edge 246, a bottom edge 248, and a bushing wall 250 extendingbetween the top and bottom edges 246, 248. The bushing sidewall 250would have an outer surface 252 to cooperatively engage internalsidewall 210 of the fusion plate 54 and an inner surface 254 tocooperatively engage the convex lower surface 242 of the head 238 of thefastener 236. The diameter 256 of the bushing may vary from the top edge246 to the bottom edge 248.

As shown, in this exemplary embodiment, the bushing is generallycylindrical in shape, but other shapes are possible. The bushing 244would have a diameter consistent with the diameter of the plate bore 214and fit between the head 238 of the fastener 236 and the internalsidewall 210 of the plate bore 214. As is conventionally known, thebushing 244 may have a gap 258 to allow the bushing 244 to be compressedand fitted into plate bore 214. Moreover, the bushing 244 may have anumber of slots 259 shown in the bottom portion of the bushing 244,which could be in the top portion of bushing 244 or a combinationthereof as well. The slots 260 allow portions of the bushing 244 to flexto facilitate implanting the fasteners 236. The bushing 244, as afastener lock, helps secure fastener 236 to plate 54.

Alternatively to bushings, the lock may be a cover plate. Referring nowto FIG. 11, a cover plate 260 is provided that is usable with the lowprofile fusion plate 200. The cover plate 260 has a first face 262 and asecond face 264 opposite the first face 262. The cover plate 260 may beshaped to fit into a recess 266 in the low profile fusion plate 200, asshown in FIG. 6. The cover plate 260, as shown, generally has a mainbody portion 268 with a cover plate bore 270, which is shown ascountersunk region 272. The cover plate bore 270 includes a shoulder 274separating a threaded portion 276 having threads T₄ of the cover platebore 276 from a non-threaded portion.

A connecting pin, which will be explained further below, couples thecover plate 260 to the low profile fusion plate 200. The cover platebore 270 aligns with the plate bore 214 described above. A plurality ofarms 278 or flared extensions 280 extend from the main body portion 268.The arms 278 extend from the main body portion a sufficient distancesuch that at least a distal end 282 of the arm extends over fastenerbore 208. The distal end 282 of the arm, thus, resists the ability ofthe fastener 236 to reverse thread from the implant. The flaredextension(s) 280 extends from the main body portion a sufficientdistance such that at least a distal end 282 of the flared extension(s)280 extends over fastener bore 208. The distal end 282 of the arm, thus,resists the ability of the fastener 236 to reverse thread from theimplant.

As can be appreciated, the shape, size, and whether arms or flaredextensions are associated with cover plate 260 depends in part on theshape and size of fusion plate 54 (shown in FIG. 1). The shape and sizeof the cover plate 260 specifically shown in FIG. 11 is designed for usewith the low profile fusion plate 200 shown in FIGS. 6 and 7. Generally,arms on cover plate 260 are associated with a single fastener bore 208and flared extension(s) 280 are associated with multiple fastener bores208.

As described above, the cover plate bore 270 generally aligns with theplate bore 214. The cover plate 260 is coupled to the low profile fusionplate 200 using a connecting pin 286 as shown in FIG. 12. The connectingpin 286 has a head 288 and a shaft 290. The head 288 has a lip 292 thatabuts either the second face 262 or, if the cover plate bore 270 iscountersunk, the shoulder 274. The shaft 290 has a proximal portion 294proximate to the head 288, a distal portion 296 distal from the head288, separated by a medial portion 298. The proximal portion 294 has afirst thread T₅ that is designed to cooperatively engage the threads T₄of the cover plate 260. The medial portion 298 is shown as beingthreadless and provides a transition from the proximal portion to thedistal portion. The distal portion 296 has a second thread T₆ that isdesigned to cooperatively engage the threads T₃ of the inner threadedbore 234 of the threaded connector 224. The connecting pin 286 haslength L₄ and couples the cover plate 260 to the low profile fusionplate 200.

Referring now to FIG. 13, a low profile implant 300 consistent with theabove is provided. The low profile implant 300 includes spacer 52 havingthe rearward portion 104 (or the anterior portion for the exemplaryspinal application) with voids 122 and 124 separated by a central strut126. The protrusions 116 are shown on the top (or superior) portion. Thecavity 120 in the rearward portion 104 has the low profile fusion plate200 therein. The fastener bores 208 of the low profile fusion plate 200are aligned, generally, with the spacer channels 144. The fasteners 236extend through the fastener bores 208, spacer channels and extend out ofthe top portion and bottom portion of the spacer 52. The cover plate 260is provided with arms 278 covering two of the fastener bores 208 andflared extensions 280 covering the other two of the fastener bores 208.The connecting pin 286 is then moved into cover plate bore 270. In aparticular embodiment, the overall height of plate 200 (measured alongthe inferior to superior direction) is similar to or the same as theoverall height of the spacer 52. In this embodiment, the implant 300 isa “zero profile” implant in that the plate 200 does not extend above orbelow the height of the disc space into which spacer 52 is disposed.

The low profile fusion plate 200 may not be usable in certain aspects ofthe technology. For example, the end plate or size of the vertebrae maynot support a fastener in such a manner, the angle necessary tofacilitate the fastener 236 extending from the rearward portion 104through the top portion 106 or bottom portion 108 may not be possible,to name but two situations in which the low profile construction asshown in FIG. 13 may not be possible or desirable. In these cases, itmay be necessary to provide a fusion plate with a slightly higherprofile than the low profile fusion plate 200, sometimes referred to asa middle profile fusion plate 400 of “single flange plate” as shown inFIGS. 14 and 15.

The middle profile fusion plate 400 has a main body portion 401 similarin construction to the low profile fusion plate 200 including a forwardface 402 and a rearward face 404 opposite the forward face 402. Asidewall 406 extends between the forward face 402 and the rearward face404. The edges of sidewall 406 may be beveled or chamfered to reducetrauma. The forward face 402 is generally sized to fit the cavity 120 ofthe spacer 52. Thus, the forward face 402 may have a length L₃, a heightH₂, and a depth D₂ to allow middle profile fusion plate to cooperativelyfit in cavity 120. The middle profile fusion plate 400 also has a firstextension side 408 that extends from the main body portion 401 beyondthe height H₂ in only one of the superior or inferior directions, whichin this exemplary embodiment, is shown as extending in the inferiordirection. A distal edge of the first extension side 408 may have aconcave shape. The first extension side 408 has an angled forward face402 and an angled rearward face 404. The first extension side 408 isangled at an angle 410 (shown in FIG. 15) with respect to the rearwardface 404 to allow for the first extension side 408 to overlap one of thebones to be fused. The angle 410 provides that the portion of firstextension side 408 distal from the rearward face 404 is offset from thespacer 52 rearward portion 104. While described as an angle forconvenience, the first extension side 408 may have a slight curvature orsinusoidal shape rather than a straight angled surface. In a particularembodiment, the first extension side 408 is curved in a manner such thatthe distal tip portion of extension side 408 is generally parallel tomain body portion 401.

As can be appreciated, the middle profile fusion plate 400 has aplurality of fastener bores 412 in the forward and rearward faces 402,404 that cooperate with spacer channels in the implant to allow a set offasteners to extend from the middle profile fusion plate 400 through thespacer 52 into the endplates of the associated vertebrae 40, 42. Whilethe spacer could be formed consistent with spacer 52 above, the spacerin this exemplary embodiment may be provided with spacer channels 144 onthe upper edge 140 and no spacer channels 144 on the lower edge 142 as adesign option.

A second plurality of fastener bores 414 are provided in the firstextension side 408. The fastener bores 414 are arranged to allow thefastener 236 to extend through the angled forward face 402 and theangled rearward face 404 directly into, for example, a pedicle of theinferior vertebrae 42. The fastener bores 412, 414 have an internalsidewall 416 forming a concave surface for cooperative engagement withthe convex lower surface 242 of head 238 of fastener 236. The middleprofile fusion plate 400 includes a plate bore 418 similar to plate bore214 to receive the threaded connector 224 that couples the middleprofile fusion plate 400 to the spacer 52.

Referring now to FIGS. 16 and 17, a perspective view and side elevationview of a middle profile cover plate 420 is shown. The cover plate 420has a first face 422 and a second face 424 opposite the first face 422,which is similar to cover plate 260 described above. The cover plate 420may be shaped to fit into a recess 426 in the middle profile fusionplate 400, as shown in FIG. 14. The cover plate 420, as shown, generallyhas a main body portion 428 with a cover plate bore 430, which may beconstructed similar to cover plate bore 270 described above to receivethe connecting pin 286 to couple the cover plate 420 to the middleprofile fusion plate 400. The middle profile fusion plate 400 comprisesa plurality of arms 432 extending at an angle 410 extending from mainbody portion 428 and a flared extension 434 extending from the main bodyportion 428. The arms 428 are angled to coincide with the angle 410 ofthe first extension side 408 such that the arms 432 extend over aportion of the fastener bores 414. The arms 432 may have a web ofmaterial (not shown) between them to form a flared extension instead ofarms as a matter of design choice. Also, the arms 432 are designed tocooperatively engage the recess 426 and, as such, may have a curvatureor sinusoidal shape.

The arms extend from the main body portion a sufficient distance suchthat at least a distal end 436 of the arm extends over fastener bores414. The distal end 436 of the arm, thus, resists the ability of thefastener 236 to reverse thread from the implant. The flared extension(s)434 extends from the main body portion a sufficient distance such thatat least distal ends 438 of the flared extension(s) 434 extend overfastener bores 412. The distal ends 438, thus, resist the ability of thefasteners 236 to reverse thread from the implant.

As can be appreciated, the shape, size, and whether arms or flaredextensions are associated with cover plate 420 depends in part on theshape and size of fusion plate 54 (shown in FIG. 1). The shape and sizeof the cover plate 420, specifically shown in FIGS. 16 and 17, isdesigned for use with the middle profile fusion plate 400 shown in FIGS.14 and 15. Generally, arms on cover plate 432 are associated with asingle fastener bore 414 and flared extension(s) 434 are associated withmultiple fastener bores 412.

Referring now to FIG. 18, a middle profile implant 450 consistent withthe above is provided. The middle profile implant 450 includes spacer 52having the rearward portion 104 (or the anterior portion for theexemplary spinal application) with voids 122 and 124 separated by acentral strut 126. The protrusions 116 are shown on the top (orsuperior) portion. The cavity 120 in the rearward portion 104 has themiddle profile fusion plate 400 therein. The fastener bores 412 of themiddle profile fusion plate 400 are aligned, generally, with the spacerchannels 144. The fasteners 236 extend through the fastener bores 412and spacer channels and extend out of the top portion and bottom portionof the spacer 52. The fastener bores 414 in the first extension side 408of the middle profile fusion plate 400 are aligned with the inferiorvertebrae 42 in this example, but the fastener bores 414 may be alignedwith the superior vertebrae 40 or other bone surfaces depending on theuse. The fasteners 236 extend through the fastener bores 414 and intothe pedicle or anterior side 46 of the inferior vertebrae 42. Dependingon the dimensions, the fasteners 236 extending through the fastenerbores 414 may not pass through spacer channels 144, and in those cases,the spacer channels may be removed. In a particular embodiment, thefasteners 236 extending through fastener bores 414 are generallyparallel to spacer 52 surface. In this manner, fasteners 236 may begenerally orthogonal to the bony surface to which they are coupled. Inalternative embodiments, fasteners 236 extending through fastener bores414 are at a diverging or converging angle relative to spacer 52 upperor lower surfaces. The cover plate 260 is provided with arms 432covering two of the fastener bores 414 and flared extensions 434covering the other two of the fastener bores 412. Generally, the arms432 are associated with the bores on the first extension side and theflared extension is associated with the bores on the remainder of thefusion plate. The connecting pin 286 couples the cover plate 420 to themiddle profile fusion plate 400.

In some applications, the middle profile fusion plate 400 may not beusable or desirable for any number of reasons. In these cases, it may benecessary to provide a fusion plate with a slightly higher profile thanthe middle profile fusion plate 400, sometimes referred to as a highprofile fusion plate 500 or “two flange plate” as shown in FIGS. 19 and20. The high profile fusion plate 500 has a main body portion 501similar in construction to the low profile fusion plate 200 including aforward face 502 and a rearward face 504 opposite the forward face 502.A sidewall 506 extends between the forward face 502 and the rearwardface 504. The edges of sidewall 506 may be beveled or chamfered toreduce trauma. The forward face 502 is generally sized to fit the cavity120 of the spacer 52. Thus, the forward face 502 may have a length L₃, aheight H₂, and a depth D₂ to allow the high profile fusion plate tocooperatively engage cavity 120.

The high profile fusion plate 500 also has a first extension side 508that extends beyond the height H₂ in one of the superior or inferiordirections, which in this exemplary embodiment is shown as extending inthe inferior direction and a second extension side 509. The first andsecond extension sides 508, 509 may be pinched such that a distal edgeof the first and second extension sides 508, 509 has a concave shape.The first extension side 508 has an angled forward face 502 ₁ and anangled rearward face 504 ₁. The second extension side has an angledforward face 502 ₂ and an angled rearward face 504 ₂. The firstextensions side 508 and the second extension side 509 are angled at anangle 510 with respect to the rearward face 504 to allow for each of thefirst and second extension sides 508, 509 to overlap opposite ones ofthe bones to be fused. The angle 510 provides that the portions of thefirst and second extension sides 508, 509 distal from the rearward face504 are offset from the spacer 52 rearward portion 104. While describedas an angle for convenience, the first and second extension sides 508,509 may have a slight curvature or sinusoidal shape rather than astraight angled surface. One or both extension sides 508, 509 may havean orientation or curvature, and/or fastener bores similar to thatdescribed for first extension side 408 above. Moreover, while describedas symmetrical, the first extension side 508 and the second extensionside 509 may be asymmetrical and may be necessarily so under certainanatomical conditions.

As can be appreciated, the high profile fusion plate 500 has a pluralityof fastener bores 512 in the first and second extension sides 508, 509that cooperate with a set of fasteners to extend from the high profilefusion plate 500 into the pedicle or anterior side of the associatedvertebrae 40, 42. While the spacer could be formed consistent withspacer 52 above, the spacer in this exemplary embodiment may be providedwithout spacer channels 144 on the upper and lower edges 140, 142 as adesign option. The fastener bores 512 have an internal sidewall 514forming a concave surface for cooperative engagement with the convexlower surface 242 of head 238 of fastener 236. The high profile fusionplate 500 includes a plate bore 518 similar to plate bore 214 to receivethe threaded connector 224 that couples the high profile plate 500 tothe spacer 52.

Referring now to FIGS. 21 and 22, a perspective view and side elevationview of a high profile cover plate 520 is shown. The cover plate 520 hasa first face 522 and a second face 524 opposite the first face 522,which is similar to cover plates 260, 420 described above. The coverplate 520 may be shaped to fit into a recess 526 in the fusion plate500, as shown in FIG. 19. The cover plate 520, as shown, generally has amain body portion 528 with a cover plate bore 530, which is may beconstructed similar to cover plate bore 270, 430 described above toreceive the connecting pin 286 to couple the cover plate 520 to the highprofile fusion plate 500.

The cover plate 520 comprises a plurality of arms 532 extending at anangle 510 extending from main body portion 528. The arms 532 are angledto coincide with the angle 510 of the first and second extension sides508, 509 such that the arms 532 extend over a portion of the fastenerbore 512. The arms 532 may have a web of material 534 there between. Theweb of material 534 may be extended from a flared extension instead ofarms as a matter of design choice. Also, the arms 532 are designed tocooperatively engage the recess 526 and, as such, may have a curvatureor sinusoidal shape. The arms extend from the main body portion asufficient distance such that at least a distal end 536 of the armextends over fastener bores 512. The distal end 536 of the arm, thus,resists the ability of the fastener 236 to reverse thread from theimplant. As shown in FIGS. 21 and 22, the distal end 536 of the arms 532may have pads 538 that extend from the arms 532 into the fastener bores512 to contact the fastener heads 238. The pads 538 shown herein may beprovided on any of the arms or flared extensions described above.

As can be appreciated, the shape, size, and whether arms or flaredextensions are associated with cover plate 520 depends in part on theshape and size of fusion plate 54 (shown in FIG. 1). The shape and sizeof the cover plate 520, specifically shown in FIGS. 21 and 22, isdesigned for use with the high profile fusion plate 500 shown in FIGS.19 and 20. Generally, arms on cover plate 520 are associated with asingle fastener bore 512 and flared extension(s) having the web ofmaterial 534 may be associated with multiple fastener bores 512.

Referring now to FIG. 23, a high profile implant 550 consistent with theabove is provided. The high profile implant 550 includes spacer 52having the rearward portion 104 (or the anterior portion for theexemplary spinal application) with voids 122 and 124 separated by acentral strut 126. The protrusions 116 are shown on the top (orsuperior) portion. The cavity 120 in the rearward portion 104 has thehigh profile fusion plate 500 therein. The fastener bores 512 in thefirst and second extension sides 508, 509 of the high profile fusionplate 500 are aligned with the pedicles or the anterior sides of theinferior and superior vertebrae 42, 40 in this example, but the fastenerbores 512 may be aligned with other bone surfaces depending on the use.The fasteners 236 extend through the fastener bores 512 and into thepedicle or anterior side 46 of the superior and inferior vertebrae 40,42. Depending on the dimensions, the fasteners 236 extending through thefastener bores 512 may not pass through spacer channels 144, and inthose cases, the spacer channels may be removed. The fasteners 236 maybe generally orthogonal to anterior sides 46 of vertebrae 40, 42, or mayalternatively enter the vertebrae at divergent or convergent angles inone or more planes. The cover plate 520 is provided with arms 532covering the fastener bores 512. The connecting pin 286 couples thecover plate 520 to the high profile fusion plate 500.

Notice that the above described implant was described with reference toa low profile fusion plate, a middle profile fusion plate, and a highprofile fusion plate. On reading the disclosure, one of ordinary skillin the art will now recognize that the use of low profile, middleprofile, and high profile are relative terms to distinguish the abovedescribed embodiments and are provided for reference and should not beconstrued to limit the technology of the present application.

The technology of the present application also includes methods forimplanting the apparatus described above. While the methodology isprovided in certain discrete steps, one of ordinary skill in the artwill recognize that the steps identified may be broken into multiplesteps or multiple steps may be combined into a single step. Moreover,the sequence of events provided may be altered or rearranged withoutdeparting from the technology of the present application. With that inmind, the surgeon would first determine the appropriate spacer to beused. In spinal applications, the spacer may be sized to restore theheight corresponding to the height of a health vertebra. In otherapplications, the spacer may be sized to most readily promote fusion orthe like.

Once the appropriate spacer is identified, the threaded connector may bethreaded into the spacer bore, although the threaded connector mayalready be threaded to the spacer. The surgeon would next implant thespacer and threaded connector to the fusion site. Notice the threadedconnector may be threaded when the spacer is in the fusion site as amatter of surgical technique. Next the surgeon would determine whether alow, middle, or high profile fusion plate is appropriate for thepatient's anatomy. The fusion plate would be coupled to the threadedconnector. For example, the protrusions on the slotted head may becompressed and fitted into the fusion bore until a snap fit is formedbetween the slotted head and the fusion plate. The fusion plate may befitted to the threaded connector such that the spacer and fusion plateare placed at the fusion site at the same time.

The surgeon would next use fasteners to couple the implant to the boneysegments, such as the superior and inferior vertebrae for a spinalapplication. Finally, a cover plate that corresponds to the fusion plateis selected and coupled to the fusion plate. For example, the connectingpin may be threaded through the cover plate bore and fusion plate boreinto the internal threads of the threaded connector to couple the coverplate, fusion plate, and spacer.

The implant may be supplemented with bone growth promoting substances tofacilitate fusion of adjacent vertebrae between spinous processes,laminae, transverse processes, facets, and/or other spinal structures.The bone growth promoting substances may be spaced from the implant,placed adjacent the implant, sandwiched between the implant andunderlying bone, placed inside the implant, coated onto the implant,and/or otherwise placed relative to the implant. If it is coated ontothe implant, it may cover the entire implant or only selected portionsof the implant such as the extensions, fasteners, spinous processcontacting portions of the spacer, and/or other portions.

As used herein, bone growth promoting substances may include bone paste,bone chips, bone strips, structural bone grafts, platelet derived growthfactors, bone marrow aspirate, stem cells, bone growth proteins, bonegrowth peptides, bone attachment proteins, bone attachment peptides,hydroxylapatite, calcium phosphate, other suitable bone growth promotingsubstances, and/or combinations thereof.

The implant and any associated cerclage or other components may be madeof any suitable biocompatible material including among others metals,resorbable ceramics, non-resorbable ceramics, resorbable polymers, andnon-resorbable polymers. Some specific examples include stainless steel,titanium and its alloys including nickel-titanium alloys, tantalum,hydroxylapatite, calcium phosphate, bone, zirconia, alumina, carbon,bioglass, polyesters, polylactic acid, polyglycolic acid, polyolefins,polyamides, polyimides, polyacrylates, polyketones, fluoropolymers,and/or other suitable biocompatible materials and combinations thereof.

Various methods, systems and devices for treating spinal fractures aredisclosed. While detailed descriptions of one or more embodiments havebeen provided above, various alternatives, modifications, andequivalents are possible. Therefore, the above description should not betaken as limiting the scope of possible embodiments, which is defined bythe appended claims.

What is claimed is:
 1. An implant configured to be interposed betweenopposing faces of two bones to be fused together, the implantcomprising: a spacer configured to fit between the opposing faces of thetwo bones to promote fusion of the two bones, the spacer having aforward portion, a rearward portion, a top portion, a bottom portion,and two side portions; the rearward portion comprising at least onecavity, the spacer having at least one spacer channel extending from therearward portion to at least one of the top portion or the bottomportion; a fusion plate coupled to the spacer, the fusion platecomprising a main body portion and a first extension side portion, themain body portion comprising a forward face, a rearward face opposed tothe forward face, and a sidewall connecting the forward face and therearward face, the forward face and at least a portion of the sidewallto be received in the at least one cavity, the first extension sideportion configured to extend beyond at least one of the top portion orthe bottom portion of the spacer, the fusion plate comprising at least afirst bore aligned with the at least one spacer channel and extendingfrom the rearward face to the forward face of the fusion plate and asecond bore in the first extension side portion extending from therearward face to the forward face; and a threaded connector having afirst end and a second end opposite the first end, the first end of thethreaded connector having external threads, the second end of thethreaded connector having outwardly turned lips and wherein the spacercomprises a threaded spacer bore in the at least one cavity and thefusion plate comprises a fusion plate bore having a shoulder, the fusionlate bore being aligned with the threaded spacer bore, such that thefusion plate is coupled to the threaded connector by causing theoutwardly turned lips to engage the shoulder and the threaded connectoris coupled to the spacer bore by threading the threaded connector intothe threaded spacer bore whereby the spacer and the fusion plate areconnected.
 2. The implant as in claim 1, further comprising a lockcoupled at least to the fusion plate, wherein the lock comprises a coverplate that covers a portion of each of a plurality of fasteners.
 3. Theimplant of claim 2, further comprising a connecting pin, wherein thecover plate comprises a cover plate bore aligned with the fusion platebore such that the connecting pin is inserted through the cover platebore and coupled to the threaded connector whereby the cover plate iscoupled to the fusion plate.
 4. The implant as in claim 3, wherein theconnecting pin has a threaded shaft and a head and wherein the threadedconnector has a bore with an internal thread such that the threadedshaft of the connecting pin threads onto the internal thread of thethreaded connector.
 5. The implant as in claim 4, wherein the threadedshaft has a first end proximate a head of the connecting pin with afirst thread and a second end distal the head of the connecting pin witha second thread and wherein the cover plate bore has a thread such thatwhen the second end of the connecting pin is threaded with the internalthread of the threaded connector, the first thread of the connecting pinthreads with the thread of the cover plate bore whereby the cover plate,fusion plate, and spacer are coupled.
 6. The implant as in claim 3,wherein the cover plate bore has a countersunk bore to receive a head ofthe connecting pin.
 7. The implant as in claim 2, wherein the fusionplate has a recess into which the cover plate fits.
 8. The implant as inclaim 2, wherein the lock comprises a bushing in at least the first boreand in at least the second bore.
 9. The implant as in claim 1, whereinthe first extension side portion comprises an angled forward facearranged at an angle and an angled rearward face, the angle configuredto allow the angled forward face to overlie one of the first or secondbones.
 10. The implant as in claim 1, comprising a protrusion extendingfrom the forward face of the fusion plate to engage the at least onespacer channel.
 11. The implant as in claim 1, wherein the at least onespacer channel is a bore.
 12. The implant as in claim 11, wherein thebore extends from the at least one cavity to the top portion.
 13. Theimplant as in claim 1, wherein the at least one spacer channel is formedin the shape of a half-cylinder and is configured to allow a fastener toextend from the at least one cavity to an endplate of a vertebra.
 14. Animplant configured to be interposed between opposing faces of two bonesto be fused together, the implant comprising: a spacer configured to fitbetween the opposing faces of the two bones to promote fusion of the twobones, the spacer having a forward portion, a rearward portion, a topportion, a bottom portion, and two side portions; the rearward portioncomprising at least one cavity, the spacer having at least one spacerchannel extending from the rearward portion to at least one of the topportion or the bottom portion, and a spacer bore having a first threadin the at least one cavity; a fusion plate comprising a main bodyportion and a first extension side portion, the main body portioncomprising a forward face, a rearward face opposed to the forward face,and a sidewall connecting the forward face and the rearward face, theforward face and at least a portion of the sidewall to be received inthe at least one cavity, the first extension side portion flaring fromthe main body portion and configured to extend beyond at least one ofthe top portion or the bottom portion of the spacer, the fusion platecomprising a plurality of fastener bores including at least a firstfastener bore aligned with the at least one spacer channel and extendingfrom the rearward face to the forward face of the fusion plate and asecond fastener bore in the first extension side portion extending fromthe rearward face to the forward face, the main body portion comprisinga plate bore aligned with the spacer bore and having a shoulder disposedtherein; a connector having a first end and a second end opposite thefirst end, the first end of the connector having second threadsconfigured to operatively engage the first thread, the second end of theconnector having a slotted head with outwardly turned lips, theconnector is coupled to the fusion plate by engaging the outwardlyturned lips with the shoulder and the connector is coupled to the spacerbore by operatively engaging the second threads of the connector withthe first thread of the spacer bore; and a cover plate coupled to thefusion plate.
 15. The implant as in claim 14, wherein the connectorcomprises an internal bore having a third thread and the cover plate iscoupled to the fusion plate by a connecting pin having a fourth threadon a shaft of the connecting pin to operatively engage the third thread.16. The implant as in claim 15, wherein the cover plate includes a coverplate bore having a fifth thread and the connecting pin comprises asixth thread located between a head of the connecting pin and the fourththread on the shaft of the connecting pin where the sixth threadoperatively engages the fifth thread to couple the connecting pin to thecover plate.
 17. The implant as in claim 16, further comprising aplurality of fasteners, wherein the plurality of fastener bores comprisean inner concave surface and the plurality of fasteners comprise a headand a shaft where the head has a convex surface to cooperatively engagethe inner concave surface of the plurality of fastener bores to allow anorientation of each of the plurality of fasteners to be adjusted.
 18. Amethod for implanting a fusion cage, the method comprising: selecting aspacer configured to fit into a space between two bones that are to befused together, the spacer having a front portion for insertion and arear portion opposite the front portion, the rear portion having arecess and a spacer bore with a first thread; threading a connector thathas a first end with an external second thread and a second end with aslotted head having an outturned lip into the spacer bore such that thesecond thread cooperatively engages the first thread; fitting a fusionplate that has a plate bore with a shoulder located in the plate boreonto the connector to cause the shoulder to cooperatively engage theoutturned lip to couple the fusion plate to the connector; threading aplurality of fasteners through the fusion plate to one of the two boneswherein at least one of the plurality of fasteners is threaded throughthe spacer; and coupling a cover plate to the fusion plate to inhibitreverse threading of the plurality of fasteners.